It is the aim of this project to develop non-invasive methods for the study of drug and steroid biotransformation in children. We will study children that have diseases or are taking medications that are known to alter the drug and steroid metabolizing capacity in adults. Several diseases states, including liver disease, endocrine disorders and an increasing number of drugs have been shown to alter the adult's capacity to metabolize drug and steroid hormones. 1. The rate of metabolism of a model drug (antipyrine) will be studied in two biological fluids, blood and saliva. Antipyrine will serve as an indicator of the rate of metabolism of a drug principally metabolized by the mixed function oxidase system in the liver microsomes. We plan to develop an RIA for antipyrine determination. 2. imultaneously, the urinary excretion of 6 beta-hydroxycortisol, the most important unconjugated metabolite of cortisol, will be measured by RIA and 6 beta-hydroxycortisol excretion may also serve as a useful, non-invasive indicator for the study of induction and inhibition of drug metabolism by drugs and hormones.